51 



VEGETABLE KINGDOM. 

 CLASS FUCOIDES. 



RUSOPHYCUS CHESTERENSE, n. Sp. 



Plate V, Fig. 1, showing three specimens on a slab. 



This plant as it appears upon the slabs consists of elongated 

 subcylindrical stems somewhat flattened upon the upper side, and 

 having a longitudinal central depression, from which rounded ribs 

 are directed diagonally at either side. The diameter of a stem is 

 about half an inch, and there are about 10 rounded ribs on either 

 side of the depression in the distance of an inch. 



Found in the Kaskaskia Group, at Chester, 111., and now in the 

 collection of Wm. F. E. Gurley. 



RUSOPHYCUS MONTANENSE, 11. Sp. 



Plate V, Fig. 2, showing a specimen on a slab. 



This plant as it appears upon the slabs consists of simple elon- 

 gated subcylindrical stems, somewhat flattened upon the upper side, 

 and having a longitudinal central depression from which rounded 

 ribs are directed diagonally at either side. The diameter of a stem 

 is a little more than half an inch, and there are about 3 rounded 

 ribs on either side in the distance of half an inch. Our two speci- 

 mens of this species are a little larger than any of our specimens 

 of R. cJtesterense, and the diagonal ribs are less numerous. 

 These characters are shown in the illustrations which fully repre- 

 sent both species. Of course these differences might be regarded as 

 only of varietal value, but as the fossils are from different Groups of 

 rocks and therefore widely separated in geological time, we prefer to 

 distinguish them as species. 



Found in the Burlington Group, in Bridger Mountains, Montana, 

 by Earl Douglass, and now in the collection of S. A. Miller. 



